The ex-Marine busted for trying to check his Indiana-registered gun at the Empire State Building got a no-jail, misdemeanor deal yesterday.

“I definitely did not know it was illegal to bring a gun into New York City,” Ryan Jerome, 29, of South Bend, said after pleading guilty in Manhattan Criminal Court, one day after nurse Meredith Graves agreed to a similar deal for trying to check her Tennessee-registered gun at the 9/11 Memorial.

Jerome had insisted he checked a gun-law reciprocity site on his smartphone, but a formatting error made it look like Indiana-registered guns are OK in New York, rather than the other way around.